A technology is conventionally known in the medium storage device, dust cover and image forming device, that a retractable extension part is provided in the removable medium storage device to store sheets that are larger than a footprint of the image forming device.
Japanese Laid-Open Patent Application No. H8-73058 describes a technology relating to an image forming device, in which a dust cover that is slidable in an installation/removal direction of a sheet cassette, which is a medium storage device, is provided above a sheet cassette exit opening and covers an opening of the sheet cassette in association with installation and removal of the sheet cassette.